Polyhalopropyl ethers and process for making them



United States Patent 3,080,428 PQLYHALGPRGPYL ETHERS AND PROCESS FQR MAKING 'El-EM Vikto: Weinrnayr, Landenhs l'g, Pa assignor to E. 1. d1 a d Nemeurs. an m n Wi min ton, Be a corporation of Delaware No'Drawing. Filed Jilly 20, 1960, Ser. No. 44,019

' 13 Claims. (Cl. 2605- 614) This invention relates to certain new symmetrical polyhalopropyl ethers in which atleast one halogen is fluorine and to a novel process for making them.

Halogenated ethers are known to be valuable for a wide variety of purposes. In general, those which contain fluorine are unsymmetrical and/or are completely halogenated. Heretofore, symmetrical partially 'halogenated ethers containing fluorine, particularly the symmetrical partially halogenated propyl ethers, have been unknown and it has not been known how to prepare them.

It is an object of this invention to provide a novel class of symmetrical partially halogenated propyl ethers containing at least one fluorine atom in the 3 position which are valuable for a wide variety of purposes. Another object is to provide a novel process for the preparation of such ethers. A further object is to,provide such a process which can be readily carried outand controlled to produce a polyhalopropylether of such class as the predominant product. A particular object is to provide such a process which employs readily available starting materials and produces the ethers in high yields and high purity and which can be practiced on alargescale without'undue hazards. Other objects are to produce new compositions of matter and advance the art. Still other objects will appear hereinafter.

The above and other objects may be accomplished in accord with this invention which comprises the novel class of symmetrical polyhalopropyl others of the formula (CXYFCHXCH O wherein each X is a member of the group consisting of hydrogen, chlorine and fluorine and Y is a halogen of an atomic number of from 9 to 17 and the process for preparing such ethers which comprises reacting about 2 moles of a haloethylene of the formula CXY=,CHX, wherein each X is a member of the group consisting of hydrogen, chlorine and fluorine and Y is a halogen of an atomic number of from 9 to 17, with 2 moles of formaldehyde in the presence of at least 2 moles of hydrogen fluoride at a temperature of from about -50 C. to about 200 .C. w l

The process of this invention is simple and easily carried out at low or moderate temperatures and pressures and produces the desired others in high yield andhigh purity from readily available starting materials. The process does not require any catalyst but takes place readily and at satisfactory rates in the absence of any added catalytic material.

The symmetrical polyhalopropyl ethers of this invention are new chemical compounds which are useful for a variety of purposes. They arenoninfiammable, noncorrosive, and stable. For example, symmetrical 3,3,3- trifiuoropropyl ether on a watch glass couldnot be ignited .with a match and, when it wasrnaintained in the presence of copper, aluminum and mild steel at 130 F. for 0 days, it was not deleteriously affected, did not corrgde the aluminum or thesteel, and caused only a sli-glrttarinish ing of the copper. They are useful as hydraulic fluids, heat transfer agents, reaction media, and solvents. They are of special value as selective solvents for the s'eparationof the components of mixtures of high. molecular weight highly fluorinatedorganic compoundsinto constituents of difiere nt fluorine content having .diilereut properties, and particularly for highly fluorinated copp er "polyhalopropylating agents "as benzeneand naphthalene, e.g., for

"ice

phth alocyanines. They are also- 'particularly valuable as i for aromatic compounds such introducing the corresponding 'polyhalopropyl groups into aromatic hydrocarbons. Furthermore, the others of this invention are intermediates for the preparation of the corresponding polyhalopropyl alcohols and may be converted to such alcohols by well-known chemical methods, such as treatin; them with concentrated sulfuric acid or concentrated phosphoric acid at elevated temperatures.

The 'haloethylenes which are employed in the process of this invention are well known compounds and are represented by the general formula CXY=CHX wherein each X is a member of the group consisting of hydrogen, chl'ofine'and fiuorine',which may be the same or different, and Y is a halogen of an atomic number of from 9 to' 17. Preferred classes of haloethylenes are those having the general formula CXY=CHX and CXY=CH wherein each df-X and Y is a halogen of an atomic number of from 9 to 17."

The reaction taking place to produce the symmetrical ethers of this invention may be represented, with 1,1- difluoroethylene as the haloethylenereactant, by the following equation:

This reaction appears to be specific to the haloethylenes above defined and is not a general reaction. For example, when unsubstituted ethylene was employed in the process of this invention, it did not produce an ether but produced l,3-dioxane. .When 1,2-dibromoethylene was employed as the haloethylene reactant in the process of this invention, it failed to react with the formaldehyde and the hydrogen fluoride. When tetrafiuoroethylene is employed .as the haloethylene reactant, it produces fluoromethyl 2,2,3,3,3 pentafiuoropropyl ether (CH FOCH CP CF and 1H,lfi pentafiuoroel propanol (CFgCFgCHQOH) as disclosed in my copending application Serial No. 814,415, filed May 20, 1959, and now Patent No. 2,992,276, and did not form a symmetrical polyhalopropyl ether of the present invention.

Representative haloethylenes that may be reacted with formaldehyde and hydrogen fluoride to produce the symmetrical polyhalopropyl ethers of this invention are listed below, together with the particular symmetrical polyhalo- .propyl ether produced from each of them.

Fluoroethylene (CI-1F=CH 3,3-difiuoropropyl ether (CHFZCHZCHZMO -1,1-diiluoroethylene (CE ,=.C H 3,3,3 trifluoropropyl I (ithr Trifluoroethylene (CF =CHF) 2,3,3,3 tetrafluoropropyl ether (CF CHFCH O Chloroethylene (CHCl=CI-I 3 chloro-3-fluoropropy1 ether (CHClFCl-I CH O 1,1-dichloroethylene (CCl =C1-I 3,3 dichloro-3-fiuomp pyl ether (CC12FCI'I2CH2)2O l,2 -f,dichloroethylene (CHCl CHCl)+2,3-dichloro-3-fl11- oropropyl ether.(CHClFCHClCH O Trichloroethylene (CCl ,=CHCl) 2,3,3rtrichloros3-fiuo- .ropropyl ether CCl FCHClCI-IQ O lrchloro-l-iluoroethylene (CClF=CH a 3-chloro- 3,3-diilu'or'opropyl' ether (CClF CH CI-I O 1,l;dichlorofiuoroethylene (CCl =CHF)- 3,3 dichloro- 2,3-difiub i oplopyl' ether .(CCl FCI-IFCHQ O 1,2 dichlorofiuoroethylene (CClF:CHCl)- 2,3-dichloro- 3,3-difiuoropropyl ether (CClF CI-IClCH O 2-chloro 1,1 dilluoroethylene (CF =CHCl) 2-chloro- 3,3,3 -trifiuoropropyl ether (CRCHClCI-l) O Thefgrmaldehyde may .beused inits unpolymerized .fprgn .pr injhe {9BR of one of its polymers, such as paraformaldehyde and trioxane, without affecting the rate or the course of the reaction. For ease of handling and for economic reasons, the formaldehyde ordinarily will be in the form of paraformaldehyde.

Preferably, the hydrogen fluoride will be anhydrous hydrogen fluoride. This is for practical reasons, such as keeping the corrosion of the equipment at a minimum. It is unnecessary to employ special precautions to maintain anhydrous conditions for the reaction to proceed satisfactorily. Water is formed as a product of the reaction. Aqueous hydrofluoric acid of 75% concentration or higher may be used. More dilute hydrofluoric acid tends to cause excessive decrease in the yield of the desired products. The anhydrous hydrogen fluoride need not be completely pure; commercial anhydrous hydrogen fluoride, which contains traces of sulfur compounds, is satisfactory. v

The amount of haloethylene required for the reaction is 2 moles per 2 moles of formaldehyde and at least 2 moles of hydrogen fluoride. Less than this amount of haloethylene results in a corresponding decrease in the production of the desired product from a given amount of formaldehyde, and more than this amount comprises an excess of the haloethylene which reacts with the excess hydrogen fluoride to produce a fluorine-containing polyhaloethane.

Although the stoichiometric equation for the reaction of this process requires only 2 moles of hydrogen fluoride for each 2 moles of formaldehyde, an excess of hydrogen fluoride which acts as a solvent for the formaldehyde and provides a reaction medium is normally employed. Usually, about 2 moles to about 10 moles of hydrogen fluoride for each mole of formaldehyde, preferably about 5 to about 7 moles of hydrogen fluoride, will be employed.

The reaction may be carried out at temperatures in the range of from about 50 C. to about 200 C. For a smooth, controlled reaction with high conversion and yield, the temperature usually will be in the range of from about 0 C. to about 100 C., preferably from about 10 C. to about 60 C. The reaction will take place at temperatures below -50 C. but the reaction rate is decreased and there is no technical need or economic justification for maintaining such low temperatures for the reaction. Also, there is no advantage in conducting the reaction above 100 C., although temperatures up to about 200 C. may be employed, if desired. When it is desired to carry out the process at atmospheric pressure, the temperatures should be maintained at about 10 C. or below, preferably from about 0 C. to about 10 C.

Preferably, the reaction is carried out at atmospheric pressure. In a closed reaction vessel, the pressure will depend partly upon the vapor pressure and amount of the haloethylene charged to the reaction vessel and partly upon the temperature at which the reaction is run. Usually, the pressure will be the autogenous pressure at the temperature employed, i.e. from about 0 p.s.i.g. (pounds per square inch gauge) to about 3000 p.s.i.g.

The process of this invention is simple and readily carried out in conventional reaction vessels that may be cooled or heated and agitated and which will withstand the pressures that may be encountered in the reaction. The reaction vessel will be constructed of, or lined with, a material or materials that are resistant to the corrosive action of anhydrous hydrogen fluoride and/or concentrated solutions of hydrofluoric acid. Suitable materials of construction include platinum, silver, nickel, stainless steel, and Hastelloy.

The process may be carried out as a batch process with the haloethylene continuously introduced into a solution of formaldehyde or of a polymer thereof in hydrogen fluoride until the formaldehyde is reacted, or with the total amount of haloethylene charged into the reaction vessel already containing the solution of formaldehyde or of its polymer in hydrogen fluoride, or as a continuous operation. In a continuous operation, for example, a stream of a solution of paraformaldehyde in anhydrous hydrogen fluoride and a stream of the haloethylene will be continuously introduced simultaneously into a reaction vessel maintained at the required reaction temperature and pressure, and a solution of the reaction products in hydrogen fluoride will be continuously withdrawn for continuous isolation of the products. In a batch process, the haloethylene is preferably introduced gradually or in small increments into the formaldehydeuhydrogen fluoride solution to avoid a rapid exothermic reaction from a mass of material that would cause the heat of reaction to build-up and make temperature and pressure control diflicult.

The symmetrical polyhalopropyl others may be isolated by conventional methods such as washing with watcr or aqueous alkali, fractional distillation, and the like, preferred methods of isolation being illustrated in Examples 1 to 8 which are given hereinafter.

In order to more clearly illustrate this invention, preferred modes of practicing it and the advantageous results obtained thereby and to also illustrate representative uses of the novel ethers of this invention, the following examples are given in which the parts are by weight except where otherwise specifically indicated:

EXAMPLE I A one-liter stainless steel reaction vessel, fitted with a mechanical agitator, was charged with 120 g. of paraformaldehyde and 560 g. of anhydrous technical hydrogen fluoride. 1,1-difluoroethylene was continuously introduced into the agitated solution of paraformaldehyde in hydrogen fluoride art such a rate that the tern eraturc of the reaction mass could be maintained between 10 C. and 6 C. by cooling the reaction vessel with a mixture of ice and salt. After about 45 minutes, gas started to be emitted from the reaction mass, indicating that the reaction to produce a polyfluorop-ropyl ether was nearing completion. The emitted gas was 1,1,1-trifluoroethane, formed by -a reaction between the 1,1-di-fluoroethylene and the hydrogen fluoride after the paraformaldehyde had been essentially consumed by reaction with the haloethylene and hydrogen fluoride. When there was no further absorption of 1,1-difluoroethylene without the emission of gas from the reaction mass, a total of 270 parts of 1,1-difluoroethylene had been added. The reaction mass was then poured into 4 kg. of an ice and water mixture. he oil that separated was washed with water until essentially acid-free. It amounted to 321 g. By steam distillation of the oil, 279 g. of unrefined 3,3,3- trifluoropropyl ether, (CF CH CH O, was obtained, 83% of which distilled upon fractionation at 114 C. to 115 C. at atmospheric pressure. The collected fractionated material was 3,3,3-trifiuoroprcpyl ether of 99% purity. The purity was determined by vapor phase chromatography and the identity was established by elemental chemical analysis, in-rrared absorption, and nuclear magnetic resonance examination.

EXAMPLE 2 In the reaction vessel of Example 1, l,1-difluoroethyl one was continuously passed into a solution of g. of paraformaldehyde in 500 g. of anhydrous technical hydrogen fluoride at -40 C., maintained with an acetone-solid carbon dioxide bath. After three hours reaction time, the paraformaldehyde was essentially consumed; gas was emitted from the reaction mass and comprised a mixture of 1,1,1-trifluoroethane and unreacted 1,1-difiuoroethylene. The reaction mass was then poured into an ice-water mixture and 309 g. of an oil separated. After water washing and steam distilling this oily product, 300 g. of unrefined 3,3,3-tri-fluoropropyl ether was. obtained.

EXAMPLE 3 In the reaction vessel of Example 1, 1,1-difiuoroethy1- ene was continuously passed into a solution of 120 g. of paraformaldehyde in 160 g. of anhydrous technical hydrogen fluoride maintained at C. until absorption of the haloethylene by the reaction mass ceased and gas began to be emitted. Upon mixing. the reaction'mass with an ice-water mixture, 299 got oil separated. 'By steam distillation, 215 g. of unrefined 3,3,3 trifi uoropropyl ether was isolated, o f which 73% distilled at 114 C. to 115 C.

EXAMP 4 A 500 ml. pressure reactor, lined with Hastelloy C, was charged with 190 g. of anhydrous technical hydrogen fluoride and 48 g. of paraformaldehyde, and the reactor and its contents were .cooled to 60- C. To the reactor was then added quickly and in a single mass 206 g. of 1,1 -difiuor0ethylene. The reactor was sealed, heated to 60 C., and kept under agitation for about one hour. Then the reactor and its contents were cooled to about 0 C., the reaction mass was poured into and mixed with ice and water, and 140 g. of oil separated. After water washing and steam distilling this oil, 106. g. of unrefined 3,3,3-triil-uoropropyl other had collected. By subsequent fractionation, pure 3,3,3-trifluoropropyl ether, having a boiling point of 114 C. to 115 C., was obtained.

EXAMPLE 5 Proceeding as in Example 4, the reactor was charged with 188 g. of an 80% aqueous hydrofluoric acid solution and g. of paraformaldehyde and cooled to -60 C. To the reactor was then added a 200 g. quantity of 1,1-difiuoroethylene. The reaction mass was heated at 80 C. for 2 hours, after which time the mass was cooled to about 0 C. and poured onto cracked ice. The 54 g. of oil that separated was steam distilled to yield 49 g. or unrefined 3,3,3-triiiuoropropyl ether. Upon fractionation, g. or pure material, having a boiling point of 114 C., was obtained.

EXAMPLE 6 A 500 ml. pressure reactor, lined with Hastelloy C, was charged with 200 g. of anhydrous technical hydrogen fluoride and 30 g. of paraformaldehyde and cooled to C. Then a 150 g. quantity of fluoroethylene was added to the reactor. Within 5 minutes, the temperature of the reaction mass rose to C., owing to the heat of reaction. The reaction mass was cooled to 0 C. and poured onto cracked ice. The separated oil was waterw-ashed and steam distilled to produce 63 g. of non' aqueous distillate. Upon fractionation, 37 g; of 3,3-difluoropropyl ether (CHF CH CH M O, having a boiling point of 147 C., was obtained. The 3,3-difluoropropyl ether was identified by chemical, infrared, and nuclear magnetic resonance analyses.

EXAMPLE 7 A one-liter stainless steel reaction vessel, fitted with a mechanical agitator, was charged wtih 60 g. of paraformaldehyde and 500 g. of anhydrous technical hydrogen fluoride and cooled to about 5 C. Over a period of ninety minutes,'242 g. of 1,1-dichloroethylene were added to the reactor while the temperature of the agitated reac tion mass was maintained between 5 C. and l0 C. The agitation was continued for about one hour after the addition of the 1,1-dichloroethylene was completed, while the temperature was kept at 10 C. to 12 C. The reaction mass was then poured onto cracked ice, and 198 g. of an oil separated. The oil was water washed and steam distilled, and 191 g. of a colorless oil was recovered.

Upon fractionation, pure 3,3-dichloro-3-fluoroproPYl ether (CCI FCH CHQ O, having a boiling pointof 119 at 19 mm. mercury pressure was obtained. The

:identity of theetherwasestablished by the analyticalprocedures used inthe preceding examples.

EXAMPLE .3

A mixture of 600. g. anhydrous technical hydrogen fluoride, 3.0 g. of paraformaldehyde, and 2.60 .g. of hichloroethylene was heated with agitation in a stainless steel pressurereactor at 50 C. ,for 6 hours. The reac- .tion mass was then mixed with an ice and water mixture, whereupon 243 g. of abrown .oil separated. After a preliminary purification by water washing and steam distilling, followed by a fractionation, pure 2,3,3 trichloro-3- fluoropropyl ether (Cl FCHClCH- O, having a. boiling .point of 100 C. ,at .3 mm. mercury pressure was ,obtained. The composition and structure. of .the product were determined by chemical, :infnared, and nuclear magnetic resonance analyses.

EXAMPLE 9 Alkylatiorr of Benzene With 3,3,3-Trifluoropropyl Ether A m e m r s n 1.4 s.- bs zn 50 o a hydrous technical hydrogen fluoride, and, 52 g. of 3,3,3- trifluoropropyl ether was heated at 200 C. for six hours in a stainless steel pressure .vlcssel. At .the end ,of this time, the reactor and its contents were cooled to about 0 C. The reaction mass was poured onto cracked ice, and the separated benzene solution of thereaction product was steam distilled. The water-insoluble distillate was dried over anhydrous magnesiumsulfate and then fractionated by distillation. After the benzene dis tilled, some unreacted 3,3,3-trifluoropr pyl ether was recovered, and, at 154 C., 3,3,3Jrifiuoropropylbenzene, identified by chemical analysis and ,nuclear magnetic resonance patterns, distilled and was collected.

EXAMPLE 1Q Separation f Fluorina e Coppe h lm ocymine A mixture of fluorinated copper phthalocyanines was prepared as described in my copending application, Serial No. 706,235, filed December 31, 195 7, and now Patent No. 3,006,921. One part of copper phthalocyaninetet'racarboxylic acid amide (made by the urea process from trirnellitic acid and cuprous chloride), 15 parts ofte'chnical anhydrous hydrogen fluoride, and 8 parts of technical sulfur tetrachloride were charged into a stainless steel bomb which had been cooled in a Dry Ice-acetone mixture and had been swept with nitrogen. 'The bomb was closed and put into an oil bath where it could be agitated. The temperature of the oil bath was raised to 150 C., over a period of about four hours, and the bomb was agitated at an oil bath'temperature of 150 :C. to 55 i h ursfler co l n h 'bom t room temperature, it was cooled further in iced water and he r ma nin pres u e m in du o n' xc of s r e a u ri ew s el asedhe'rca t on 'ma wa h p u e o t abou 200 'pa t o ice, fi te e washed nearly acid free, slurried in 'ZOO'parts of dilute aqueous ia qn u ra ize all hyd g n f u ri e, filt re an washed again with water, and dried .at' C to C. The p bl e solidthuso tai e was extracted ith acetone to give a bluefsoluticnf.Uponlevaporation of the a tone. on pa o m tu o coppe polyflu p wv( r fleg o hrl)pli ha o ya "bt" I Th s ace o eclublclnnx Yd about 80 C. with symmetr cal 13.3.3- fl ibmnrcpy em een soluti n fo med o'l 'e insq u' ma e ia Thesolusol e t The fiuo p opyl e her-soluble traction dissolved in these ,solvents to give .grcenycolorcd solutions. The-rcasondonthe different .colors of .the solutions lies a sence in the difference in the fluorine content of the different fractions. The fluorinated copper phthalocyanines, that are insoluble in the 3,3,3-trifluoropropyl ether and produce blue solutions in acetone, had a nitrogen atom to fluorine atom ratio of 8:13, while the trifluoropropyl ether-soluble green solution material had a nitrogen to fluorine ratio of 8:18. The symmetrical 3,3,3-trifluoropropyl ether gave a' distinctly cleaner separation of the mixture of fluorinated copper phthalocyanines than could be obtained with benzene. Also, symmetrical 2,3,3- ichloro-3-fluoropropyl ether was found to have a selective solvent action on said mixture of fluorinated copper phthalocyan-ines.

Also, for purposes of convenience, the haloethylenes, the amounts of the reagents, the conditions employed, and the products obtained in the examples, are summerized in the following Table 1.

m from 9 to 17, with 2 moles of formaldehyde in the presence of from about 5 to about 10 moles of anhydrous hydrogen fluoride at a temperature of from about 50 C. to about 200 C.

7. The process for preparing a symmetrical polyhalopropyl ether which comprises reacting about 2 moles of a haloethylene of the formula CXY -CHX, wherein each X and Y is a halogen of an atomic number of from 9 to 17, with 2 moles of formaldehyde in the presence of at least 2 moles of anhydrous hydrogen fluoride at a temperature of from about C. to about 100 C.

8. The process for preparing a symmetrical polyhalopropyl ether which comprises reacting about 2 moles of a haloethylene of the formula CXY CHX, wherein each X and Y is a halogen of an atomic number of from 9 to 17, with 2 moles of formaldehyde in the presence of from about to about moles of anhydrous hydrogen fluoride TABLE I Szmmiary of Examples Ex- Ethylenic Reactant Grams HCHO, HF, Temp., Pressure Product B.P., O. ample grams grams C.

1 LI-difluoro-ethyleue.. 271 120 560 (CF3CH1CH2)2O 114-115. 2 "d0 120 500 (OF3CHQOHQ)2O 114-115. 3. do 120 160 (ONCE- 011920 114-115. 4- do 206 48 100 (CF5CH2CI'Iz)zO. 114-115. 5.. (lO-- 200 1 188 (CFzCH2(3 lz)2Q- 114415. 6. Iluoroethylene 150 130 200 (CHF2CH2CH2)ZO 147. 7. 1,1-dichloro-ethylene 242 60 r 500 (CCI FCH CHQMO 119 at 19 mm 8 Trichloroethylene 260 30 600 Autogenous. (OCl2FCHC1C1Ifl)20-. 100 at 3 mm. 9 Alkylatiou of benzene with 3,3,Z-trifiuorcpropyl ether. 10-. Separation of fluorinated copper phthaloeyanincs.

X 80% hydrofluoric acid solution.

It will be understood that the preceding examples have been given for illustrative purposes solely and that this invention is not limited to the specific embodiments described therein. On the other hand, it will be readly apparent that, subject to the limitations set forth in the general description, many variations can be made in the materials, proportions, conditions, and techniques employed without departing from. the spirit or scope of the invention.

From the preceding description and examples, it will be apparent that this invention provides a novel process which is simple and easy to carry out on a large scale without undue hazards and which can be readily controlled to produce the desired products in high yields and purity from readily available starting materials. The invention further provides a novel class of symmetrical polyhalopropyl ethers which are valuable for a variety of useful purposes. Accordingly, it will be apparent that this invention constitutes a valuable advance in and contribution to the art.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A symmetrical polyfluo-ropropyl ether of the formula (CXF CHXCHQ O wherein each X is a member of the group consisting of hydrogen and fluorine.

2. Symmetrical 2,3,3,3-tetrafluoropropyl ether.

3. Symmetrical 3,3,3-trifluoropropyl ether.

4. Symmetrical 3,3-difluoropropyl ether.

5. The process for preparing a symmetrical polyhalopropyl ether which comprises reacting about 2 moles of a haloethylene of the formula CXY=CHX, wherein each X is a member of the group consisting of hydrogen, chlorine and fluorine and Y is a halogen of an atomic number of from 9 to 17, with 2 moles of formaldehyde in the presence of at least 2 moles of hydrogen fluoride at a temperature of from about C. to about 200 C.

6. The process for preparing a symmetrical polyhalopropyl ether which comprises reacting about 2 moles of a haloethylene of the formula CXY=CHX, wherein each X is a member of the group consisting of hydrogen, chlorine and fluorine and Y is a halogen of anatomic number of I i at a temperature of from about 0 C. to about 60 C.

9. The process for preparing a symmetrical polyhalopropyl ether which comprises reacting about 2 moles of trichloroethylene with 2 moles of formaldehyde in the presence of from 2 to about 10 moles of anhydrous hydrogen fluoride at a temperature of from about 0 C. to about C.

10. The process for preparing a symmetrical polyhalopropyl ether which comprises reacting about 2 moles of a halo ethylene of the formula CXY CH wherein each of X and Y is a halogen of an atomic number of from 9 to 17, with 2 moles of formaldehyde in the presence of from 2 to about 10 moles of anhydrous hydrogen fluoride at a temperature of from about 0 C. to abot 100 C.

11. The process for preparing symmetrical 3,3,3-trifluoropropyl ether which comprises reacting 1,1-difiuoroethyh ene with 2 moles of formaldehyde in the presence of at least 2 moles of hydrogen fluoride at a temperature of from about 50 C. to about 200 C.

12. The process for preparing symmetrical 3,3,3-trifluoropropyl ether which comprises reacting 1,1-difluoroethylene with 2 moles of formaldehyde in the persence of from 2 to about 10 moles of hydrogen fluoride at a temperature of from about 0 C. to about 100 C.

13. The process for preparing symmetrical 3,3,3-trifluoropropyl ether which comprises reacting 1,1-d-ifluoroethyl ene with 2 moles of formaldehyde in the presence of from about 5 to about 10 moles of anhydrous hydro-gen fluoride at a temperature of from about 0 C. to about 10 C. at atmospheric pressure.

References Cited in the file of this patent UNITED STATES PATENTS Zisman et a1. Feb. 18, 1958 

1. A SYMMETRICAL POLYFLUOROPROPYL ETHER OF THE FORMULA (CXF2CHXCH2)2O WHEREIN EACH X IS A MEMBER OF THE GROUP CONSISTING OF HYDROGEN AND FLUORINE. 